Novel structural analogs of corosolic acid having anti-diabetic and anti-inflammatory properties

ABSTRACT

This invention relates to novel corosolic acid analogs of the formula I, wherein R 1 , R 2 , R 3 , R 4  and R 5  are as indicated below in each of said analogs: 1. R 1 =COCH 3 , R 2 =R 3 =R 4 =H, R 5 =COOH or R 1 , =R 3 =R 4 =H, R 2 =COCH 3 , R 5 =COOH 2. R 1 =R 2 =COCH 3 , R 3 =R 4 =H, R5=COOH 3. R 1 =COC 5 H 4 N, R 2 =R 3 =R 4 =H, R 5 =COOH 4. R 1 =COCH 2 NH 2 .HC 1 , R 2 =R 3 =R 4 =H, R 5 =COOH 5. R 1 =COCH 2 (CH 3 )NH 2 .HC 1 , R 2 =R 3 =R 4 =H, R 5 =COOH 6. R 1 =COCH:CHC 6 H 2 (OCH 3 ) 3 , R 2 =R 3 =R 4 =H, R 5 =COOCH 3  7. R 1  &amp; R 2 =S0 2 , R 3 =R 4 =H, R 5 =COOH 8. R 1 =R 2 =R 3 =R 4 =H, R 5 =CONH 2  9. R 1 =R 2 =R 3 =R 4 =H, R 5 =CONHC 6 H 5  10. R 1 =R 2 =R 3 =R 4 =H, R 5 =CONHCH 2 CH 2 NH 2  11. R 1 =R 2 =R 3 =R 4 =H, R 5 =CON(CH2CH 2 ) 2 NH 12. R 1 =R 2 =R 3 =R 4 =H, R 5 =CONHCH 2 CH 2 0H 13. R 1 =R 2 =R 3 =R 4 =H, R 5 =COOCH 3  14. R 1 =R 2 =COCH 3 , R 3 =R 4 =H, R 5 =COOCH 3  15. R 1 =R 2 =H, R 3  &amp; R 4 =0, R 5 =COOCH 3  16. R 1 =R 2 =COCH 3 , R 3  &amp; R 4 =0, R 5 =COOCH 3  17. R 1 =R 2 =H, R 3  &amp; R 4 =0, R 5 =COOH 18. R 1 =R 2 =COCH 3 , R 3  &amp; R 4 =0, R 5 =COOH 19. R 1  &amp; R 2 =S0 2 , R 3  &amp; R 4 =0, R 5 =COOH 20. R 1 =R 2 =H, R 3  &amp; R 4 =0, R 5 =CONH 2  21. R 1 =R 2 =R 3 =H, R 4 =OH, R 5 =CONH 2  22. R 1 =R 2 =R 3 =H, R 4 =OH, R 5 =COOCH 3  23. R 1 =R 2 =R 3 =R 4 =H, R 5 =CH 2 0H 24. R 1 =R 2 =R 3 =R 4 =H, R 5 =CHO 25. R 1 =R 2 =R 3 =R 4 =H, R 5 =COOCOC 6 H 2 (OCH 3 ) 3  26. R 1 =R 2 =R 3 =H, R 4  &amp; R 5 =OCO. These compounds exhibit good hypoglycemic and 5-lipoxygenase inhibitory activities. They also inhibit tumour growth. Pharmaceutical compositions containing known adjutants and the title compound are also within the scope of this invention.

This invention relates to novel structural analogs of corosolic acidhaving anti-diabetic and anti-inflammatory properties. These compoundsare found to exhibit potent hypoglycemic, 5-lipoxygenase inhibitory andantitumor activities.

TECHNICAL FIELD

Diabetes is perceived as a disorder of metabolism, where body's naturalability to utilize food that has been broken down by digestion isvitiated. The body utilizes glucose, a major metabolic product fromfood, for energy and for cell growth. Glucose disperses throughout thebody through the blood stream and enters cells with the help of ahormone called insulin. Insulin is produced by pancreas, a large glandbeneath the stomach. In people with diabetes mellitus, either thepancreas does not produce enough insulin to move the glucose into thecells or the cells do not respond to the insulin, even though plenty isproduced (Reaven, G. M., Role of insulin resistance in human disease;Diabetes, 1998, 37, 1595-1607). As a result of this impairment, glucosebuilds up in the blood stream and excreted out of the body without everhaving been used as fuel.

Untreated diabetes can lead to very serious chronic problems, includingheart disease, kidney failure, blindness, nerve damage and amputations(Porte, D. et al., Science, 1996, 27, 699-700). Many experts believethat diabetes, cardiovascular disease and obesity all have a commonfactor linked by a condition called insulin resistance also known asSyndrome X (Bagchi, D., Syndrome X, The Diabetes, CVD and Obesity link,Health Products Business, June 2001, 62.). But with proper management,the risk of such problems can be greatly reduced. The management plandepends on the type of diabetes: insulin-dependent diabetes mellitus(IDDM) or noninsulin-dependent diabetes mellitus (NIDDM).

BACKGROUND ART

There are a number of agents currently available in the market fordiabetes management, which belongs to various structural types. Forexample, thiazolidinediones, sulfonyl ureas, alpha-glucosidaseinhibitors and biguanides are some of the drug types currently availablein the market. According to the American Diabetes Association, diabetesmellitus is estimated to effect 6% of the world population and therecent studies indicate that the number of diabetic patients could riseto 300 million by 2025. Worldwide sales of antidiabetic drugs reached 10billion US dollars in 2002. Oral antidiabetics accounted for 63% ofthese sales and glucophase (metformin) was the leading product. Withrising number of people suffering from diabetes worldwide, the marketfor diabetes medications could exceed $ 20 billion by 2006. In thenatural products arena, a handful of herbal medications were proven tobe effective against this terrible menace. For example, Fenugreek(Trigonella foenumgraecum), Gymnema (Gymnema sylvestre), Jamun/Jambolan(Syzygium cumini), Bitter melon/Karela (Momordica charantia) and Banaba(Lagerstroemia speciosa) are some of the products known to showhypoglycemic activity. Natural antidiabetic treatments have gainedpopularity in the recent years because of their proven safety from longhistory of usage in traditional medicine and also present usage inherbal treatments. Banaba, Lagerstroemia speciosa L, has gotten theworldwide attention in the past few years as organic insulin. It iswidely distributed in Philippines, as well as in Malaysia, South Chinaand tropical Australia. Corosolic acid or colosolic acid(2α-hydroxyursolic acid, CAS No. 4547-24-4), a triterpenoid compoundisolated from the banaba extract was found to be responsible for theantidiabetic activity. Banaba has long been recognized for the treatmentof diabetes and also for maintenance of low blood pressure and improvedkidney function in Philippines and other East Asian countries. Clinicalstudies confirmed the hypoglycemic effects of corosolic acid (Judy, W.V. et. al., J. Ethnopharmacol., 2003, 87(1), 115-7). Indian species ofLagerstroemia (Lagerstroemia parviflora, Lagerstroemia indica,Lagerstroemia speciosa, etc), which grows along east coast from Orissato West Bengal, also produce corosolic acid. Matsuyama, U.S. Pat. No.6,485,760 (2002) described the blood sugar lowering effect ofLagerstroemia extract.

Presently, there has been a tremendous surge in the demand fornon-steroidal, plant based anti-inflammatory agents. 5-Lipoxygenase isthe key enzyme for the biosynthesis of leukotrienes and 5(S)-HETE, theimportant mediators, for inflammatory, allergic and obstructive process,from arachidonic acid. 5-Lipoxygenase is the target enzyme foridentifying inhibitors, which have the potential to cope with a varietyof inflammations and hypersensitivity-based human diseases includingasthma, arthritis, bowl diseases such as ulcerative colitis andcirculatory disorders such as shock and ischaemia. Scientists around theworld have invested major effort during the last ten years, inidentifying 5-lipoxygenase inhibitors from plant sources. Gum resin ofBoswellia species known as Indian frankincense has been used as ananti-inflammatory agent in traditional Ayurvedic Medicine in India. Thesource of anti-inflammatory actions has been attributed to boswellicacids (Safayhi, H., et al., Planta Medica, 1997, 63, 487-493 and J.Pharmacol. Exp. Ther., 1992, 261, 1143-46, both the journals publishedfrom USA), a group of triterpene acids isolated from the Boswellia resin(Padhy, R. S., et al., Indian J. Chem., 1978, 16B, 176-178). During oursearch for new anti-inflammatory agents, we have observed, to the bestof our knowledge for the first time that corosolic acid is a potentialinhibitor of 5-LOX. The inhibitory activity was found to be on par with3-O-acetyl-11-keto-β-boswellic acid (AKBA).

The olenane and ursane triterpenoids also gained prominence recently fortheir antiproliferative actions. As 5-lipoxygenase (5-LOX) is the firstenzyme in the metabolic pathway leading to the formation of leukotrienesand eicosanoids that are important in carcinogenesis process, inhibitorsof 5-LOX may thus have profound influence on the growth and apoptosis ofvarious cancer lines (Yong S. Park, et. al., Planta Medica, 2002, 68,397-401). Boswellic acids, for example inhibited several leukemia celllines in vitro and inhibited melanoma growth and induced apoptosis(Hostanska, K., et. al., Anticancer Res., 2002, 22(5), 2853-62). Theacetyl boswellic acids were found to be unique class of dual inhibitorsof human topoisomerages I and II α (Syrovets, T. et. al., Mol.Pharmacol., 2000, 58(1), 71-81). A number of oleanane and ursanetripenoids were found to be powerful inhibitors of nitric oxideproduction in macrophases, which can be correlated to their cancerchemoprevention activity (Honda, T. et. al., J. Med. Chem., 2000, 43,1866-77). Corosolic acid, which has the gross structure very similar toAKBA and other ursane derivatives, may thus hold promise as an antitumoragent.

OBJECTS OF THE INVENTION

The present invention was aimed at producing novel analogs of corosolicacid for structure-activity relationship studies. The main objective wasto make analogs with enhanced water solubility and increasedhypoglycemic activity. The functional groups that can be expended tomake new analogs are carboxyl group, trisubstituted double bond andvicinal diol. The hydroxyl groups found utility to couple with moietieslike natural acids and aminoacids, which not only improves watersolubility but also presumed to enhance the biological recognition tothe parent compound in the transport process.

The acid function was utilized to attach highly polar amine moietiesthrough an amide linkage. The same group can also be utilized to makeester compounds by reacting with alcohols or halides. The lower alkylesters can be reduced with LAH (lithium aluminum hydride) to introducean additional alcohol group as depicted in structure 23. Oxidizingagents suitable for allylic oxidation, such as chromium trioxide can beutilized to generate 11-ketocorosolic acid compounds. Allylic oxidationusing NBS (N-bromosucinimide) however yielded a lactone 26. Theacylation transformation can be controlled to yield monoacylatedcompounds or diacylated compound by limiting the quantities of acylatingagent. The general strategy to attach amino acid unit was coupling ofBOC (tert-butoxycarbonyl) protected amino acids like glycine and alanineetc. to corosolic acid using DCC (1,3-dicyclohexylcarbodiimide), DMAP[4-(dimethylamino)-pyridine] followed by deprotection of BOC group usingHCl/dioxane to yield glycyl and alanyl derivatives, respectively, ofcorosolic acid.

SUMMARY OF THE INVENTION

This invention relates to a novel structural analogs of corosolic acidhaving the general formula I

wherein R₁, R₂, R₃, R₄ and R₅ are as indicated below in each of saidanalogs:

-   -   1. R₁=COCH₃, R₂=R₃=R₄=H, R₅=COOH or R₁=R₃=R₄=H, R₂=COCH₃,        R₅=COOH    -   2. R₁=R₂=COCH₃, R₃=R₄=H, R₅=COOH    -   3. R₁=COC₅H₄N, R₂=R₃=R₄=H, R₅=COOH    -   4. R₁=COCH₂NH₂.HCl, R₂=R₃=R₄=H, R₅=COOH    -   5. R₁=COCH(CH₃)NH₂.HCl, R₂=R₃=R₄=H, R₅=COOH    -   6. R₁=COCH:CHC₆H₂(OCH₃)₃, R₂=R₃=R₄=H, R₅=COOCH₃    -   7. R₁ & R₂=SO₂, R₃=R₄=H, R₅=COOH    -   8. R₁=R₂=R₃=R₄=H, R₅=CONH₂    -   9. R₁=R₂=R₃=R₄=H, R₅=CONHC₆H₅    -   10. R₁=R₂=R₃=R₄=H, R₅=CONHCH₂CH₂NH₂    -   11. R₁=R₂=R₃=R₄=H, R₅=CON(CH₂CH₂)₂NH    -   12. R₁=R₂=R₃=R₄=H, R₅=CONHCH₂CH₂OH    -   13. R₁=R₂=R₃=R₄=H, R₅=COOCH₃    -   14. R₁=R₂=COCH₃, R₃=R₄=H, R₅=COOCH₃    -   15. R₁=R₂=H, R₃ & R₄=O, R₅=COOCH₃    -   16. R₁=R₂=COCH₃, R₃ & R₄=O, R₅=COOCH₃    -   17. R₁=R₂=H, R₃ & R₄=O, R₅=COOH    -   18. R₁=R₂=COCH₃, R₃ & R₄=O, R₅=COOH    -   19. R₁& R₂=SO₂, R₃& R₄=O, R₅=COOH    -   20. R₁=R₂=H, R₃ & R₄=O, R₅=CONH₂    -   21. R₁=R₂=R₃=H, R₄=OH, R₅=CONH₂    -   22. R₁=R₂=R₃=H, R₄=OH, R₅=COOCH₃    -   23. R₁=R₂=R₃=R₄=H, R₅=CH₂OH    -   24. R₁=R₂=R₃=R₄=H, R₅=CHO    -   25. R₁=R₂=R₃=R₄=H, R₅=COOCOC₆H₂(OCH₃)₃    -   26. R₁=R₂=R₃=H, R₄ & R₅=OCO

BRIEF DISCLOSURE OF THE INVENTION

Identification of corosolic acid analogs having the above substituentsand establishing their potent antidiabetic and anti-inflammatory actionhave been achieved by the applicants.

The corosolic acid (purity >95%) used in this study was obtained fromthe leaves of Lagerstroemia speciosa, using solvent extraction,chromatography over silica gel column and crystallization.

A further aspect of the present invention is a pharmaceuticalformulation comprising a compound as described above in apharmaceutically acceptable carrier (e.g., an aqueous or a non aqueouscarrier).

A still further aspect of the present invention is a method of treatingdiabetes, comprising administering to a human or animal subject in needthereof a treatment effective amount (e.g., an amount effective totreat, slow the progression of, etc.) of a compound as described above.

The pharmaceutical compositions of the “compound” as used herein,includes the pharmaceutically acceptable salts of the compound.Pharmaceutically acceptable salts are salts that retain the desiredbiological activity of the parent compound and do not impart undesiredtoxicological effects. Examples of such salts are (a) base additionsalts formed from metal hydroxides, NH₄OH, alkyl amines,pharmaceutically useful amine compounds etc. (b) acid addition saltsformed with inorganic acids, for example hydrochloric acid, hydrobromicacid, sulfuric acid, phosphoric acid etc. on amine compounds representedby the formula I.

Active compounds of the present invention may be produced by theprocedures described herein or variations thereof, which will beapparent to those skilled in the art. The intermediates useful forproducing the compounds of the formula I, described herein are also anaspect of the present invention, as are methods useful for producingsuch intermediates and active compounds.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is explained in greater detail in the followingnon-limiting examples.

Example 1

2-O-Acetylcorosolic acid and 3-O-acetylcorosolic acid (1): To an icecold solution of corosolic acid (500 mg, 1.06 mmol) in pyridine (0.75mL, 9.7 mmol) was added slowly acetic anhydride (0.1 mL) and continuedthe stirring for 2 h. The mixture was poured into crushed ice andvigorously stirred. The solid was filtered, washed with water, dried andsubjected to silica gel column chromatography using hexane-ethyl acetate(10%) mixture as eluent to furnish a white solid (220 mg); IR (KBr):3434, 2927, 2863, 1722, 1695, 1456, 1256, 1030 cm⁻¹; It is a mixture of3-O-acetyl and 2-O-acetyl derivatives in the ratio 1:2.7. NMR datacorresponds to major product (2-O-acetyl derivative); ¹H NMR (400 MHz,CDCl₃) δ 0.78 (3H, s, CH₃), 0.84 (3H, d, J=6.0 Hz, CH₃), 0.86 (6H, s,2×CH₃), 0.95 (3H, d, J=4.8 Hz, CH₃), 1.06 (3H, s, CH₃), 1.08 (3H, s,CH₃), 2.06 (3H, s, —COCH₃), 2.20 (1H, d, J=11.3 Hz, H-18), 3.20 (1H, d,J=10.0 Hz, H-3), 4.92-4.98 (1H, m, H-2), 5.24 (1H, br s, H-12); NMR datacorresponds to minor product (3-O-acetyl derivative): 2.14 (s, —COCH₃),3.78-3.82 (m, H-2), 4.50 (d, J=10.0 Hz, H-3), 5.24 (br s, H-12); LCMS(negative ion mode): m/z 513 (M−H)⁻.

3-O-Acetylcorosolic acid: IR (KBr): 3442, 2933, 2869, 1729, 1696, 1629,1456, 1374, 1253, 1038 cm⁻¹; LCMS (negative ion mode): m/z 513 (M−H)⁻.

Example 2

2,3-Di-O-acetylcorosolic acid (2): To a solution of corosolic acid (800mg) in pyridine (5 mL) was added acetic anhydride (5 mL) and kept at rtfor 16 h. The reaction mixture was worked up under the conditions notedin example 1, to give the diacetate, 2 (650 mg, 69%), m.p. 236-240° C.;IR (KBr): 3448, 2944, 2873, 1743, 1698, 1455, 1371, 1250, 1038, 962cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.77 (3H, s, CH₃), 0.85 (3H, d, J=6.3Hz, CH₃), 0.90 (6H, s, 2×CH₃), 0.95 (3H, d, J=5.9 Hz, CH₃), 1.07 (6H, s,2×CH₃), 1.97 (3H, s, —COCH₃), 2.05 (3H, s, —COCH₃), 2.19 (1H, d, J=11.2Hz, H-18), 4.75 (1H, d, J=10.3 Hz, H-3), 5.07-5.13 (1H, m, H-2), 5.24(1H, br s, H-12); LCMS (negative ion mode): m/z 555 (M−H)⁻.

Example 3

2-O-Nicotinoylcorosolic acid (3): To a mixture of corosolic acid (250mg, 0.53 mmol), nicotinic acid (200 mg, 1.62 mmol) and DMAP (catalytic)in acetonitrile (50 mL) was added DCC (400 mg, 1.94 mmol) and stirred atrt for 24 h. The solids were filtered off and the solvent wasevaporated. The residue was chromatographed over silica gel column usingchloroform-methanol (20%) as eluent to furnish 2-O-nicotinoylcorosolicacid (33 mg, 11%), which was crystallised from chloroform-hexane, m.p.212-216° C.; IR (KBr): 3434, 2928, 2871, 1722, 1594, 1456, 1288, 1132,955 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.81 (3H, s, CH₃), 0.84 (3H, d,J=6.3 Hz, CH₃), 0.92 (3H, s, CH₃), 0.95 (3H, d, J=6.3 Hz, CH₃), 1.11(6H, s, 2×CH₃), 1.12 (3H, s, CH₃), 3.39 (1H, d, J=9.9 Hz, H-3),5.24-5.27 (1H, br s, H-12), 7.37-7.41 (1H, m, Ar—H), 8.29 (1H, d, J=7.7Hz, Ar—H), 8.78 (1H, d, J=3.5 Hz, Ar—H), 9.22 (1H, s, Ar—H); LCMS(negative ion mode): m/z 576 (M−H)⁻.

Example 4

2-O-Glycylcorosolic acid hydrochloride (4): A mixture of corosolic acid(200 mg, 0.42 mmol), BOC protected glycine (82 mg, 0.47 mmol) and DMAP(30 mg) in dry dioxane (2 mL) at 0° C. was treated with DCC (130 mg,0.63 mmol) under vigorous stirring. After 3 h, the reaction mixture wasworked up as described in example 3, to give 2-O—(N—BOC-glycyl)corosolicacid (200 mg).

A solution of 2-(N—BOC-glycyl)corosolic acid (200 mg) in CH₂Cl₂ (2 mL)was cooled to 0° C. and treated slowly with 2 mL of 1 N HCl in dioxane.After 30 min, the stirring was continued at rt for another 2 h. Thereaction mixture was diluted with hexane (5 mL) and the precipitatedsolid was filtered, washed with hexane and dried to afford a whitepowder of 2-O-glycylcorosolic acid hydrochloride (190 mg), m.p. 268-272°C.; IR (KBr): 3432, 2979, 2926, 2859, 1749, 1690, 1461, 1243, 1050 cm⁻¹;¹H NMR (400 MHz, CD₃OD) δ 0.82-1.14 (7×CH₃), 2.2 (1H, brd, J=10.0 Hz),3.80 (1H, brm, H-3), 3.88 (2H, s, OCOCH ₂NH₃Cl), 4.66 (1H, d, J=9.9 Hz,H-2), 5.24 (1H, m, H-12), LCMS (positive ion mode): m/z 530 (M-Cl)⁺.

Example 5

2-O-Alanylcorosolic acid hydrochloride (5): A mixture of corosolic acid(500 mg, 1.06 mmol), BOC protected alanine (240 mg, 1.23 mmol) and DMAP(75 mg) in dry dioxane (2 mL) at 0° C. was treated with DCC (327 mg,1.59 mmol) under the conditions noted in example 4, obtained2-O—(N—BOC-alanyl)corosolic acid (320 mg). This was deprotected as inexample 4, to give 2-O-alanylcorosolic acid hydrochloride (250 mg) aswhite powder, m.p. 234-238° C.; IR (KBr): 3433, 2928, 2859, 1740, 1692,1621, 1459, 1369, 1245, 1107, 1041 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆) δ0.57-1.35 (24H, m, 8×CH₃), 4.68-4.76 (1H, br s, —CH—N), 4.88-5.05 (1H,br s, H-3), 5.08-5.20 (1H, br s, H-12), 8.10-8.60 (3H, br s, NH₃ ⁺);LCMS (positive ion mode): m/z 544 (M−Cl)⁺.

Example 6

Methyl 2-O-(3,4,5-trimethoxycinnamoyl)corosolate (6): To a mixture ofmethyl corosolate (100 mg, 0.21 mmol), 3,4,5-trimethoxycinnamic acid (73mg, 0.31 mmol) and DMAP (12 mg, 0.1 mmol) in CH₂Cl₂ (1.5 mL) cooled inan ice-water bath was added slowly DCC (85 mg, 0.41 mmol) in 0.5 mL ofCH₂Cl₂. The mixture was allowed to reach ambient temperature andcontinued the stirring. After 2 h, the mixture was worked-up under theconditions noted in example 4, to finish methyl2-O-(3,4,5-trimethoxycinnamoyl)corosolate (90 mg, 62%), m.p. 198-206°C.; IR (neat): 3460, 2927, 2854, 1717, 1632, 1583, 1457, 1263, 1098,1024, 805 cm⁻¹; LCMS (positive ion mode): m/z 729 (M+Na)⁺.

Example 7

2α,3β-Dihydroxyurs-12-en-28-oic acid 2,3-cyclicsulphate (7): To amixture of corosolic acid (200 mg, 0.42 mmol)) and pyridine (0.34 mL,4.2 mmol) in THF (1.5 mL) was slowly added thionyl chloride (40 μL, 4.2mmol) and stirred at rt for 2 h. The reaction mixture was poured into0.2N HCl (20 mL). The white precipitate was filtered, washed with waterand dried under vacuum. This sulphite (100 mg) was dissolved inacetonitrile (1 mL), water (0.8 mL) and CH₂Cl₂ (1 mL) and treated with asolution of ruthenium trichloride monohydrate (100 μg) in acetonitrile(1 mL) followed by NaIO₄ (300 mg). The stirring was continued for 36 h.The mixture was poured into water and extracted with ethyl acetate. Theorganic layer was washed with brine, dried over Na₂SO₄ and evaporated.The residue (90 mg) was subjected to silica gel column chromatographyusing hexane-ethyl acetate (20%) as eluent to furnish cyclicsulphatederivative 7 (40 mg), m.p. 182-186° C.; IR (neat): 3431, 2926, 2871,1693, 1459, 1386, 1211, 995, 959 cm⁻¹. LCMS (negative ion mode): m/z 533(M−H)⁻;

Example 8

Corosolamide (8): A mixture of diacetylcorosolic acid (300 mg) andthionyl chloride (2 mL) was refluxed for 1 h and the excess reagent wasremoved under reduced pressure to give acid chloride. This crude acidchloride in THF (1 mL) was added drop wise to a stirred solution ofconc. ammonia (5 mL) at ice-cold temperature for 5 min and continuedstirring at the same temperature for 2 h. The reaction mixture waspoured into ice-cold water and extracted with ethyl acetate. The organiclayer was washed with dil. H₂SO₄, water, brine and dried over sodiumsulfate. The solution was filtered and the solvent evaporated to givediacetyl corosolamide (300 mg). A solution of diacetyl corosolamide (300mg) and methanolic-potassium hydroxide (4%, 25 mL) was refluxed for 1 h.The solvent was evaporated under reduced pressure and diluted withice-cold water and acidified with dil. H₂SO₄. The solution was extractedwith ethyl acetate and the organic layer was washed with water, brineand dried over sodium sulfate. The residue obtained after evaporation ofthe solvent was chromatographed over silica gel column usingchloroform-methanol (10%) as eluent to furnish corosolamide (200 mg,67%), which was recrystallised from chloroform-hexane, m.p. 208-210° C.;IR (KBr): 3495, 2927, 2870, 1671, 1602, 1457, 1376, 1049, 959 cm⁻¹; ¹HNMR (400 MHz, CDCl₃) δ 0.83 (3H, s, CH₃), 0.86 (3H, s, CH₃), 0.87 (3H,d, J=6.7 Hz, CH₃), 0.96 (3H, br s, CH₃), 1.00 (3H, s, CH₃), 1.04 (3H, s,CH₃), 1.11 (3H, S, CH₃), 3.00 (1H, d, J=9.4 Hz, H-3), 3.67-3.73 (1H, m,H-2), 5.32 (1H, br s, H-12), 5.85 (2H, br s, CONH₂); LCMS (negative ionmode): m/z 470 (M−H)⁻.

Example 9

N-Phenylcorosolamide (9): Reaction of diacetylcorosolyl chloride (100mg) with aniline (1 mL) in THF (10 mL) and triethyl amine (1 mL) underthe conditions noted in example 8 gave N-phenylcorosolamide, which wascrystallised from chloroform-methanol (60 mg, 61%), m.p. 168-174° C.; IR(KBr): 3408, 2927, 2868, 1652, 1599, 1529, 1502, 1442, 1312, 1235, 1048cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.70 (3H, s, CH₃), 0.80 (3H, s, CH₃),0.93-1.02 (12H, m, 2 methyl singlets merge with 2 methyl doublets), 1.14(3H, s, CH₃), 3.00 (1H, d, J=7.76 Hz, H-3), 3.6-3.7 (1H, br. s, H-2),5.45-5.50 (1H, br s, H-12), 7.07 (1H, br s, Ar—H), 7.28 (1H, br s,Ar—H), 7.44 (2H, br s, Ar—H), 7.67 (1H, br s, Ar—H); LCMS (positive ionmode): m/z 548 (M+H)⁺.

Example 10

N-(2-Aminoethyl)corosolamide (10): Reaction of diacetylcorosolylchloride (200 mg) with ethylene diamine (1.0 g) in THF (10 mL) andwork-up under the conditions noted in example 8 furnishedN-(2-aminoethyl)corosolamide (110 mg, 60%), m.p. 118-120° C.; IR (KBr):3403, 2926, 1633, 1527, 1454, 1383, 1048 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆)δ 0.69 (3H, s, CH₃), 0.72 (3H, s, CH₃), 0.84 (3H, d, J=6.0 Hz, CH₃),0.92-0.94 (9H, 2 br s, 2 methyl singlets and a methyl doublet), 0.99(2H, d, J=7.2 Hz, —NCO—CH₂—), 1.05 (3H, s, CH₃), 2.17 (1H, d, J=11.2 Hz,H-18), 2.57 (2H, q, J=7.0 Hz, NH₂—CH₂), 2.70 (2H, t, J=6.7 Hz, NH₂—CH₂),2.75 (1H, d, J=9.2 Hz, H-3), 4.3-4.4 (1H, m, H-2), 5.23 (1H, br s,H-12); LCMS (positive ion mode): m/z 515 (M+H)⁺.

Example 11

N-(Corosolyl)piperazine (11): Reaction of diacetylcorosolyl chloride(100 mg) with piperazine (200 mg) in THF (10 mL) and triethyl amine (2mL) and work-up under the conditions noted in example 8 gaveN-(corosolyl)piperazine, which was crystallised from chloroform-hexane(50 mg, 52%), m.p. 226-230° C.; IR (KBr): 3434, 2924, 2868, 1628, 1455,1226, 1049 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.76 (3H, s, CH₃), 0.83 (3H,s, CH₃), 0.87 (3H, d, J=6.3 Hz, CH₃), 0.94 (3H, d, J=6.2 Hz, CH₃), 0.99(3H, s, CH₃), 1.03 (3H, s, CH₃), 1.08 (3H, s, CH₃), 2.44 (1H, d, J=8.6Hz, H-18), 2.83 (4H, s, N—CH₂), 3.00 (1H, d, J=9.5 Hz, H-3), 3.58 (4H,d, J=3.4 Hz, N—CH₂), 3.66-3.72 (1H, m, H-2), 5.23 (1H, br s, H-12); LCMS(positive ion mode): m/z 541 (M+H)⁺.

Example 12

N-(2-Hydroxyethyl)corosolamide (12): Reaction of diacetylcorosolylchloride (100 mg) with 2-aminoethanol (1 mL) in THF (10 mL) and triethylamine (1 mL) under the conditions noted in example 8 gaveN-(2-hydroxyethyl)corosolamide, which was crystallised fromchloroform-hexane to obtain 12 (43 mg, 47%), m.p. 152-158° C.; IR (KBr):3408, 2963, 2926, 2856, 1632, 1529, 1455, 1262, 1094, 1026, 802 cm⁻¹; ¹HNMR (400 MHz, CDCl₃) δ 0.81 (3H, s, CH₃), 0.83 (3H, s, CH₃), 0.87 (3H,d, J=6.2 Hz, CH₃), 0.96 (3H, br s, CH₃), 1.00 (3H, s, CH₃), 1.04 (3H, s,CH₃), 1.11 (3H, s, CH₃), 2.98 (1H, br s), 3.00 (1H, d, J=9.3 Hz, H-3),3.21-3.26 (1H, m), 3.44-3.49 (1H, m, H-2), 3.68 (3H, br s, N—CH₂CH₂—),5.34 (1H, s, H-12), 6.34 (1H, br s); LCMS (negative ion mode): m/z 514(M−H)⁻.

Example 13

Methyl corosolate (13): A mixture of corosolic acid (2.0 g, 4.34 mmol),iodomethane (1 mL, 16 mmol), potassium carbonate (4.5 g, 32.6 mmol) andacetone (60 mL) was stirred at rt for 16 h. After completion of thereaction, the solids were filtered off and the solvent was evaporatedunder reduced pressure. The residue was chromatographed over silica gelcolumn using chloroform-methanol (10%) as eluent to furnish methylcorosolate (1.7 g, 83%), which was recrystallised fromchloroform-hexane, m.p. 208-210° C.; IR (KBr): 3432, 2946, 2872, 1728,1455, 1230, 1197, 1049 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.75 (3H, s,CH₃), 0.83 (3H, s, CH₃), 0.85 (3H, d, J=6.5 Hz, CH₃), 0.94 (3H, d, J=5.7Hz, CH₃), 0.99 (3H, s, CH₃), 1.03 (3H, s, CH₃), 1.08 (3H, s, CH₃), 2.23(1H, d, J=11.0 Hz, H-18), 3.0 (1H, d, J=8.4 Hz, H-3), 3.60 (3H, s,—COOCH₃), 3.62-3.71 (1H, m, H-2), 5.25 (1H, t, J=3.4 Hz, H-12); LCMS(negative ion mode): m/z 485 (M−H)⁻.

Example 14

Methyl diacetylcorosolate (14): Reaction of diacetylcorosolic acid (500mg, 0.9 mmol) with iodomethane (0.25 mL, 4.0 mmol), potassium carbonate(1.0 g, 7.2 mmol) and acetone (25 mL) under the conditions noted inexample 13 gave methyl diacetylcorosolate (0.4 g, 78%), which wascrystallised from aq. methanol to obtain 14, m.p. 138-140° C.; IR (KBr):2943, 1742, 1243, 1036, 964 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.75 (3H,s), 0.85 (3H, d, J=6.4 Hz), 0.90 (3H, s), 0.91 (3H, s), 0.94 (3H, d,J=5.9 Hz), 1.07 (6H, s), 1.97 (3H, s), 2.05 (3H, s), 2.23 (1H, d, J=11.4Hz, H-18), 3.60 (3H, s), 4.75 (1H, d, J=10.3 Hz, H-3), 5.07-5.14 (1H, m,H-2), 5.23-5.24 (1H, m. H-12); LCMS (positive mode): 594 (M+1)⁺.

Example 15

Methyl 11-ketocorosolate (15): Methyl corosolate (400 mg) was acetylatedusing pyridine (0.5 mL) and acetic anhydride (0.5 mL) under theconditions noted in example 2 to furnish methyl diacetylcorosolate (450mg), which was dissolved in 1,4-dioxane (16 mL) and treated withN-bromosuccinimide (472 mg), water (1.6 mL) and calcium carbonate (472mg). The reaction mixture was subjected to vigorous stirring for 3 h,and then filtered. The mother liquor was poured into cold water andextracted with ethyl acetate. The organic layer was washed with brine,dried over sodium sulfate and evaporated. The residue (360 mg) inmethanol (2 mL) was added 8N KOH solution (1 mL) and stirred at 65° C.for 1 h, then poured into ice cold water, acidified with 2N HCl andextracted with ethyl acetate. The organic layer was washed with brine,dried over sodium sulfate and evaporated. The residue (340 mg) waspurified over silica gel column using hexane-ethyl acetate (25%) aseluent to furnish methyl 11-ketocorosolate (240 mg), m.p. 101-105° C.;IR (neat): 3416, 2926, 2858, 1728, 1659, 1457, 1388, 1201, 1048 cm⁻¹; ¹HNMR (400 MHz, CDCl₃) δ 0.84 (3H, s, CH₃), 0.87 (3H, d, J=6.5 Hz, CH₃),0.91 (3H, s, CH₃), 0.97 (3H, d, J=6.3 Hz, CH₃), 1.05 (3H, s, CH₃), 1.19(3H, s, CH₃), 1.30 (3H, s, CH₃), 2.35 (1H, s), 2.42 (1H, d, J=10.9 Hz),3.02 (1H, d, J=9.5 Hz), 3.16 (1H, dd, J=12.6 & 4.3 Hz), 3.61 (3H, s,CH₃), 3.77 (1H, m, H-2), 5.61 (1H, s, H-12); LCMS (positive ion mode):m/z 501 (M+H)⁺.

Example 16

Methyl diacetyl-11-ketocorosolate (16): Reaction of methyldiacetylcorosolate, (500 mg, 0.9 mmol) in 1,4-dioxane (20 mL) withN-bromosuccinimide (0.75 g, 4.2 mmol) and calcium carbonate (0.75 g, 7.5mmol) in water (2 mL) under the conditions noted in example 15 gavemethyl diacetyl-11-ketocorosolate (300 mg, 59%), which was crystallizedfrom aq. methanol to obtain 16, m.p. 264-266° C.; IR (KBr): 2952, 1734,1660, 1241, 1038, 985 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.86 (3H, d, J=6.4Hz), 0.89 (3H, s), 0.91 (3H, s), 0.93 (3H, s), 0.97 (3H, d, J=6.3 Hz),1.25 (3H, s), 1.29 (3H, s), 1.95 (3H, s), 2.04 (3H, s), 3.18 (1H, dd,J=12.8, 4.6 Hz, H-18), 3.60 (3H, s), 4.72 (1H, d, J=10.3 Hz, H-3),5.20-5.26 (1H, m, H-2), 5.61 (1H, s, H-12); LCMS (positive ion mode):m/z 608 (M+H)⁺.

Example 17

11-Ketocorosolic acid (17): A mixture of corosolic acid (400 mg, 0.85mmol), pyridine (0.4 mL, 5.1 mmol) and acetic anhydride (1.5 mL, 15.2mmol) was stirred at rt for 6 h. To the cooled reaction mixture afterdiluting with acetic acid (1.5 mL) and acetic anhydride (2 mL) was addedchromium trioxide (254 mg) and stirred for 5 h. The reaction mixture waspoured into ice-cold water and the precipitated solid was filtered andwashed with water. The solid in methanol (4 mL) was treated with 8N KOH(2 mL) and stirred at rt for 14 h and then the mixture was filteredthrough celite. The mother liquor was poured into ice water, acidifiedand extracted with ethyl acetate. The organic layer was washed withbrine, dried over sodium sulphate and evaporated. The residue (390 mg)was purified over silica gel column using hexane-ethyl acetate (30%) aseluent to furnish 11-ketocorosolic acid (60 mg), m.p. 238-242° C.; IR(neat): 3417, 2927, 2857, 1692, 1659, 1460, 1386, 1051, 974 cm⁻¹; LCMS(negative ion mode): m/z 485 (M−H)⁻.

Example 18

Diacetyl-11-ketocorosolic acid (18): Reaction of diacetyl corosolic acid(500 mg, 0.9 mmol) in dichloroethane (2 mL), acetic acid (2 mL) andwater (1 mL) with a solution of chromium trioxide (1.5 g, 15 mmol),acetic acid (2 mL) and water (2 mL) under the conditions noted inexample 17 gave diacetyl-11-ketocorosolic acid (200 mg, 39%), which wascrystallized from chloroform-hexane to obtain 18, m.p. 318-320° C.; IR(KBr): 3184, 2975, 1742, 1641, 1253, 1036 cm⁻¹; ¹H NMR (400 MHz, CDCl₃)δ 0.86 (3H, d, J=6.4 Hz), 0.90 (3H, s), 0.91 (6H, s), 0.98 (3H, d, J=6.2Hz), 1.26 (3H, s), 1.30 (3H, s), 1.95 (3H, s, —OCOCH₃), 2.05 (3H, s,—OCOCH₃), 3.18 (1H, dd, J=12.7, 3.2 Hz, H-18), 4.72 (1H, d, J=10.3 Hz,H-3), 5.19-5.26 (1H, m, H-2), 5.61 (1H, s, H-12); LCMS (negative mode):569 (M−H)⁻.

Example 19

2α,3β-Dihydroxyurs-12-en-11-one-28-oic acid 2,3-cyclicsulphate (19): Toa mixture of corosolic acid-2,3-sulfite (1.1 g, 2.12 mmol),dichloromethane (7 mL) and acetonitrile (4 mL) was added rutheniumchloride (2 mg) in acetonitrile (2 mL), followed by sodium periodate(1.5 g). After stirring the mixture at rt for 2 h, an additional amount(0.5 g) of sodium periodate was added and after 2 h of stirring, thereaction mixture was worked up under the conditions noted in example 7to give 2,3-cyclicsulphate derivative 19 (600 mg), m.p. 210-216° C.; IR(neat): 3429, 2924, 2356, 1705, 1658, 1618, 1380, 1206 cm⁻¹; ¹H NMR (400MHz, DMSO-d₆) δ 0.82 (3H, d, J=6.3 Hz, CH₃), 0.90 (3H, s, CH₃), 0.94(3H, s, CH₃), 0.95 (3H, d, J=6.4 Hz, CH₃), 1.07 (3H, s, CH₃), 1.20 (3H,s, CH₃), 1.31 (3H, s, CH₃), 3.20 (1H, dd, J=11.6 & 4.2 Hz, H-18), 4.63(1H, d, J=10.4 Hz, H-3), 5.20-5.30 (1H, m, H-2), 5.44 (1H, s, H-12);LCMS (negative ion mode): m/z 547 (M−H)⁻.

Example 20

11-Ketocorosolamide (20): Diacetyl-11-ketocorosolyl chloride (preparedfrom the 11-ketoacid, 150 mg and thionyl chloride 2 mL) was dissolved inTHF (2 mL) and the solution was added dropwise to a stirred solution ofconc. ammonia (5 mL) at ice cold temperature for 5 min and the solutionwas stirred at the same temperature for 2 h. The reaction mixture wasworked up as described in example 8 to furnish 11-ketocorosolamide (40mg, 31%), m.p. 220-222° C.; IR (KBr): 3427, 2970, 2930, 2871, 1659,1459, 1384, 1200, 1048, 971 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆) δ 0.72 (3H,s, CH₃), 0.82 (3H, d, J=6.3 Hz, CH₃), 0.89 (3H, s, CH₃), 0.93 (3H, s,CH₃), 0.95 (3H, d, J=6.3 Hz, CH₃), 1.08 (3H, s, CH₃), 1.27 (3H, s, CH₃),2.32 (1H, s), 2.36 (1H, d, J=11.1 Hz, H-18), 2.75 (1H, dd, J=12.7 & 4.2Hz), 2.86 (1H, dd, J=12.7 & 4.2 Hz), 3.48 (1H, br s, H-2), 4.23 (1H, d,J=3.8 Hz), 4.34 (1H, d, J=3.8 Hz), 5.47 (1H, s, H-12), 6.83 (1H, s, OH),6.97 (1H, s, OH); LCMS (positive ion mode): m/z 486 (M+H)⁺.

Example 21

11-Hydroxycorosolamide (21): To a magnetically stirred ice cold (10-15°C.) solution of 11-ketocorosolamide (50 mg, 0.10 mmol) in ethanol (10mL) was added sodium borohydride (200 mg, 5.26 mmol) and the solutionwas slowly brought to rt and stirred for 14 h. After completion of thereaction, the mixture was poured into ice-cold water and acidified withdil HCl. The solution was extracted with ethyl acetate and the organiclayer was washed with water, brine and dried over sodium sulfate. Theresidue obtained after evaporation of the solvent was chromatographedover silica gel column using chloroform-methanol (95:5) as eluent togive 11-hydroxycorosolamide (20 mg, 40%), which was crystallised fromchloroform-methanol, m.p. 196-198° C.; IR (KBr): 3432, 2929, 1659, 1600,1383, 1048, 968 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆) δ 0.73 (3H, s, CH₃),0.77 (3H, s, CH₃), 0.90-0.94 (9H, m, 2 methyl doublets and a methylsinglet), 1.02 (3H, s, CH₃), 1.11 (3H, s, CH₃), 2.11 (1H, d, J=10.7 Hz,H-18), 2.42-2.46 (1H, m), 2.73 (1H, dd, J=9.1 & 3.7 Hz, H-3), 3.42 (1H,m, H-2), 4.01-4.03 (2H, m, H-11 & 11-OH), 4.15 (1H, br s, NH₂), 4.28(1H, br s, NH₂), 5.17 (1H, s, H-12), 6.68 (1H, s, OH), 6.73 (1H, s, OH);LCMS (negative ion mode): m/z 486 (M−H)⁻.

Example 22

Methyl 11-hydroxycorosolate (22): To a magnetically stirred ice cold(10-15° C.) solution of methyl 11-ketocorosolate (360 mg, 0.72 mmol) inethanol (40 mL) was added sodium borohydride (1.0 g, 26 mmol) and thesolution was slowly brought to rt and stirred for 14 h. After completionof the reaction, the mixture was worked up as described in example 21 togive methyl 11-hydroxycorosolate (32 mg), m.p. 148-152° C.; IR (Neat):3416, 2927, 2872, 1719, 1648, 1455, 1388, 1220, 1146, 1047, 999, 960,770 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.86 (6H, s, 2×CH₃), 0.95 (3H, d,J=6.0 Hz, CH₃), 1.01-1.03 (12H, 3 methyl singlets and a methyl doublet),2.31 (1H, d, J=11.3 Hz, H-18), 2.44 (1H, dd, J=12.0 & 4.2 Hz), 3.02 (1H,d, J=9.3 Hz, H-3), 3.80-3.83 (1H, m, H-2), 4.39 (1H, m, H-11), 5.35 (1H,d, J=3.8 Hz, H-12); LCMS (negative ion mode): m/z 501 (M−H)⁻.

Example 23

Corosolinol (23): To an ice cold dispersion of lithium aluminum hydride(97 mg) in THF (3 mL) was slowly added methyl corosolate (500 mg) in THF(1 mL) and stirred for 2 h. The reaction mixture was diluted with ethylacetate (3 mL) and poured into ice water. The mixture was acidified with2 N HCl and extracted with ethyl acetate (50 mL). The organic layer waswashed with brine, dried over Na₂SO₄ and evaporated. The residue (400mg) was chromatographed over silica gel column using hexane-ethylacetate (80:20) as eluents to yield corosolinol (220 mg), m.p. 140-146°C.; IR (neat): 3392, 2926, 2867, 1619, 1456, 1388, 1047, 1024, 760 cm⁻¹;¹H NMR (400 MHz, CDCl₃) δ 0.81 (3H, d, J=5.4 Hz, CH₃), 0.84 (3H, s,CH₃), 0.94 (3H, d, J=5.3 Hz, CH₃), 0.99 (3H, s, CH₃), 1.03 (3H, s, CH₃),1.04 (3H, s, CH₃), 1.11 (3H, s, CH₃), 2.03 (1H, dd, J=12.3 & 4.5 Hz),3.01 (1H, d, 3=9.6 Hz), 3.19 (1H, d, J=11.0 Hz), 3.53 (1H, d, J=11.0Hz), 3.70 (1H, m, H-2), 5.15 (1H, t, J=3.4 Hz, H-12); LCMS (negative ionmode): m/z 457 (M−H)⁻.

Example 24

Corosolinal (24): To a cooled solution of Dess-Martin Periodinane (23mg) in CH₂Cl₂ (2 mL) was slowly added corosolinol (20 mg) dissolved inCH₂Cl₂ (2 mL) and the solution was allowed to ambient temperature andcontinued the stirring for 2 h. The mixture was diluted with Et₂O (20mL) and poured into an ice-cold mixture of Na₂S₂O₃.5H₂O (90 mg) insaturated aqueous NaHCO₃ (5 mL). The layers were separated and theorganic layer was washed with saturated aqueous NaHCO₃ (10 mL), water(20 mL), brine (20 mL) and dried over MgSO₄. The solution was filteredand evaporated to give corosolinal (15 mg) as a colorless oil. IR(neat): 3433, 2925, 2855, 1721, 1451, 1387, 1094 cm⁻¹; LCMS (negativeion mode): m/z 455 (M−H)⁻.

Example 25

Corosolyl tri-O-methylgallate (25): A mixture of tri-O-methylgallic acid(200 mg, 0.9 mmol) and SOCl₂ (0.5 mL) was refluxed for 0.5 h. The excessreagent was removed under high vacuum and the residue in CH₂Cl₂ (1 mL)was added to a mixture of corosolic acid (200 mg, 0.42 mmol) and DMAP(30 mg) in dioxane (5 mL). The reaction mixture was stirred at rt for 2h and then poured into ice-cold water. The mixture was extracted withethyl acetate (60 mL) and the organic layer was washed with 0.1 N HCl(40 mL), water (40 mL), brine and dried over Na₂SO₄. The residueobtained after evaporation of the solvent was chromatographed oversilica gel column using hexane-ethyl acetate (85:15) as eluent to yieldcorosolyl tri-O-methylgallate (25) as a white solid (75 mg), m.p.158-162° C.; IR (KBr): 3439, 2930, 2853, 1793, 1728, 1627, 1584, 1460,1336, 1233, 1129, 1019 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.83 (3H, s,CH₃), 0.89 (3H, s, CH₃), 0.99 (3H, s, CH₃), 1.04 (3H, s, CH₃), 1.13 (3H,s, CH₃), 1.25 (3H, s, CH₃), 2.35 (1H, s), 2.30 (1H, d, J=11.0 Hz), 3.00(1H, d, J=9.3 Hz), 3.70 (1H, brm), 3.90 (9H, s, 3×CH₃), 5.37 (1H, s,H-12), 7.28 (2H, s, Ar—H); LCMS (positive ion mode): m/z 689 (M+Na)⁺.

Example 26

2α,3β-Dihydroxyurs-12-en-11,28-olide (26): To a solution of corosolicacid (200 mg) in dioxane (6 mL) and water (0.6 mL) was added NBS (188mg) and CaCO₃ and the mixture stirred at rt for 4 h. The mixture waspoured in to ice water (30 mL) and extracted with ethyl acetate (2×30mL). The combined organic layer was washed with water (30 mL) followedby brine and dried over Na₂SO₄. The solvent was evaporated and theresidue was subjected to silica gel column chromatography using hexaneand ethyl acetate mixtures as eluents to obtain the lactone, 26 as asemisolid (60 mg); IR (neat): 3339, 2925, 2854, 1763, 1465 1261, 1021cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 0.75-1.25 (7×CH₃), 3.02 (1H, br s), 3.75(1H, brm), 5.56 (1H, brd, J=8.2 Hz), 5.98 (1H, brd, J=8.2 Hz); LCMS(negative ion mode): m/z 469 (M−H)⁻.

Hypoglycemic activity: Hypoglycemic activity was tested by theinhibition of sucrose-induced raise in serum glucose levels (SGL), bythe test substances in Albino wistar rats. The procedure involvesfasting the rats for overnight at ad libitum water, numbered weighed andrandomly divided into groups of six animals each. Prior to treatmentblood samples were drawn from sinus orbital plexus of all animals usingheparin coated glass capillaries under mild ether anesthesia. The bloodsamples were tested for serum glucose levels using enzymatic GOD/PODmethod. Optical densities were measured at 500 nm, SGL was calculated asfollows. SGL=(test OD/Standard OD)×100 and the results were expressed inmg/dL. All the groups were treated orally with corresponding testsubstances, standard, vehicle (5% gum acacia). After 30 minutes, allanimals were given 20 mL/kg of 20% sucrose solution orally using gastrictube. One hour after treatment, blood samples were drawn again undermild ether anesthesia and tested for serum glucose levels in a sameprocedure as described above for initial serum glucose estimation. Thedata was subjected to statistical treatment using t-test and inhibitoryrate was calculated by comparing mean increase in serum glucose levelsof control and treated groups.

5-Lipoxygenase activity: The corosolic acid analogs were screened fortheir 5-Lipoxygenase inhibitory potential using colorimetric method. Theassay mixture contained 50 mM phosphate buffer pH 6.3, 5-Lipoxygenase,various concentrations of test substances in dimethyl sulphoxide andlinoleic acid in a total volume of 0.5 mL, after 5 min incubation ofabove reaction mixture, 0.5 mL ferric xylenol orange reagent was addedand OD was measured after two minutes at 585 nm using spectrophotometer.Controls were run along with test in a similar manner except usingvehicle instead of test substance solution. Percent inhibition wascalculated by comparing absorbance of test solution with that ofcontrol.

Brine shrimp lethality: Brine shrimp (Artemia salina) nauplii werehatched using brine shrimp eggs in a conical shaped vessel (1 L), filledwith sterile artificial sea water (prepared using sea salt 38 g/L andadjusted to pH 8.5 using 1 N NaOH) under constant aeration for 48 h.After hatching, 10 nauplii were drawn through a pepette and placed ineach vial containing 4.5 mL brine solution and added variousconcentrations of drug solutions and volume was made upto 5 mL usingbrine solution and maintained at 37° C. for 24 h under the light ofincandescent lamps and surviving larvae were counted. Each experimentwas conducted along with control (vehicle treated), at variousconcentrations of the test substance in each set that contains 6 tubesand the average results are reported. The percentage lethality wasdetermined by comparing the mean mortal larvae of test and controltubes. LC₅₀ values were obtained from the plot of concentration (μg) vs.percentage lethality. Podophyllotoxin was used as a positive control.

The corosolic acid analogs of this invention are found to show betterhypoglycemic activity (Table 1; hypoglycemic activity is expressed inserum glucose level inhibitory rate values; higher the inhibitory ratevalue, higher is the activity) than the corosolic acid.

The corosolic acid analogs of this invention are found to show good5-lipoxygenase activity (Table 2; 5-lipoxygenase activity is expressedin % of inhibition at 100 μM and 250 μM; higher the % inhibitory values,higher is the activity).

The corosolic acid analogs of this invention are found to showsignificant brine shrimp lethality (Table 3; brine shrimp lethality isexpressed in LC₅₀ at μM concentration; lower the LC₅₀ value, higher isthe activity). TABLE I Hypoglycemic activity Oral dose SGL Inhibitory S.No Comp. No. in mg/Kg (mean ± SE) rate t-value 1 Control 5% GA 134.56 ±1.47 2 Corosolic 1 mg 121.43 ± 6.27 9.78 2.04 acid 3 1 1 mg 109.54 ±2.80 32.75 13.83 4 3 1 mg 115.86 ± 3.77 13.9 4.62 5 4 1 mg 119.23 ± 9.5826.8 4.39 6 5 1 mg 113.49 ± 4.11 22.39 7.68 7 6 1 mg 114.15 ± 6.62 21.944.78 8 8 1 mg 110.14 ± 3.18 18.15 6.97 9 9 1 mg 117.97 ± 0.37 27.5816.78 10 10 1 mg 113.57 ± 3.80 30.28 10.64 11 11 1 mg 107.88 ± 4.6119.83 5.51 12 12 1 mg 103.49 ± 7.12 36.47 7.82 13 13 1 mg 118.94 ± 8.6111.6 1.79 14 15 1 mg 120.79 ± 4.85 17.4 5.11 15 17 1 mg 120.90 ± 9.6625.78 4.19 16 19 1 mg 129.16 ± 4.66 11.67 3.56 17 20 1 mg 142.81 ± 7.3012.33 2.58 18 21 1 mg 121.57 ± 2.62 25.37 11.08 19 23 1 mg 113.06 ± 2.6130.59 13.40 20 25 1 mg 131.84 ± 7.77 9.84 1.83 21 26 1 mg 136.03 ± 4.436.97 2.23

TABLE 2 5-Lipoxygenase inhibitory activity % inhibition of 5-Loxactivity at various concentrations S. No Comp. No. 100 μM 250 μM 1Corosolic acid 13.48 29.26 2 1 15.47 24.05 3 2 20.08 44.54 4 3 28.5453.19 5 4 17.04 27.83 6 5 29.14 67.03 7 6 — 13.47 8 7 — 16.90 9 8 26.1351.29 10 9 8.16 21.77 11 10 21.74 40.87 12 11 35.42 64.99 13 12 17.7432.96 14 13 17.3 40.04 15 14 — 1.9 16 15 — 25.09 17 16 — 3.82 18 19 —11.81 19 20 18.57 42.79 20 21 25.57 50.83 21 22 24.56 49.40 22 23 2.9119.63 23 25 — 38.83 24 26 — 10.47 25 AKBA 17.45 25.3 26 NDGA 70.4 91.55AKBA: Acetyl ketoboswellic acidNDGA: Nordihydroguaiaretic acid

TABLE 3 Brine Shrimp Lethality Test S. No Compound No. LC₅₀ (μM) 1Corosolic acid 3.0 2 1 9.7 3 2 1.8 4 3 86.6 5 4 3.9 6 5 3.4 7 6 >200 8 715.0 9 8 29.0 10 9 >100 11 10 97.2 12 11 9.2 13 12 >100 14 13 10.2 15 1442.1 16 15 40.9 17 16 82.3 18 18 87.7 19 19 >100 20 20 >100 21 21 >10022 22 19.9 23 23 30.7 24 25 >200 25 26 87.0 26 podophyllotoxin 7.7

1. Novel corosolic acid analogs represented by the general formula I,

wherein R₁, R₂, R₃, R₄ and R₅ are as indicated below in each of saidanalogs:
 1. R₁=COCH₃, R₂=R₃=R₄=H, R₅=COOH or R₁=R₃=R₄=H, R₂=COCH₃,R₅=COOH
 2. R₁=R₂=COCH₃, R₃=R₄=H, R₅=COOH
 3. R₁=COC₅H₄N, R₂=R₃=R₄=H,R₅=COOH
 4. R₁=COCH₂NH₂.HCl, R₂=R₃=R₄=H, R₅=COOH
 5. R₁=COCH(CH₃)NH₂.HCl,R₂=R₃=R₄=H, R₅=COOH
 6. R₁=COCH:CHC₆H₂(OCH₃)₃, R₂=R₃=R₄=H, R₅=COOCH₃ 7.R₁ & R₂=SO₂, R₃=R₄=H, R₅=COOH
 8. R₁=R₂=R₃=R₄=H, R₅=CONH₂ 9.R₁=R₂=R₃=R₄=H, R₅=CONHC₆H₅
 10. R₁=R₂=R₃=R₄=H, R₅=CONHCH₂CH₂NH₂ 11.R₁=R₂=R₃=R₄=H, R₅=CON(CH₂CH₂)₂NH
 12. R₁=R₂=R₃=R₄=H, R₅=CONHCH₂CH₂OH 13.R₁=R₂=R₃=R₄=H, R₅=COOCH₃
 14. R₁=R₂=COCH₃, R₃=R₄=H, R₅=COOCH₃ 15.R₁=R₂=H, R₃ & R₄=O, R₅=COOCH₃
 16. R₁=R₂=COCH₃, R₃ & R₄=O, R₅=COOCH₃ 17.R₁=R₂=H, R₃ & R₄=O, R₅=COOH
 18. R₁=R₂=COCH₃, R₃ & R₄=O, R₅=COOH
 19. R₁&R₂=SO₂, R₃& R₄=O, R₅=COOH
 20. R₁=R₂=H, R₃ & R₄=O, R₅=CONH₂ 21.R₁=R₂=R₃=H, R₄=OH, R₅=CONH₂
 22. R₁=R₂=R₃=H, R₄=OH, R₅=COOCH₃ 23.R₁=R₂=R₃=R₄=H, R₅=CH₂OH
 24. R₁=R₂=R₃=R₄=H, R₅=CHO
 25. R₁=R₂=R₃=R₄=H,R₅=COOCOC₆H₂(OCH₃)₃
 26. R₁=R₂=R₃=H, R₄ & R₅=OCO
 2. The corosolic acidanalog of the formula I, as claimed in claim 1, wherein R₂ is COCH₃ andR₁, R₃, R₄ are H, and R₅ is COOH, which is 3-O-acetyl corosolic acid(1).
 3. The corosolic acid analog of the formula I, as claimed in claim1, wherein R₁ is COC₅H₄N, R₂, R₃ and R₄ are H, and R₅ is COOH, which is2-O-nicotinoylcorosolic acid (3).
 4. The corosolic acid analog of theformula I, as claimed in claim 1, wherein R₁ is COCH₂NH₂.HCl, R₂, R₃, R₄are H, and R₅ is COOH, which is 2-O-glycylcorosolic acid hydrochloride(4).
 5. The corosolic acid analog of the formula I, as claimed in claim1, wherein R₁ is COCH(CH₃)NH₂.HCl, R₂, R₃, R₄ are H, and R₅ is COOH,which is 2-O-alanylcorosolic acid hydrochloride (5).
 6. The corosolicacid analog of the formula I, as claimed in claim 1, wherein R₁ isCOCH═CHC₆H₂(OCH₃)₃, R₂, R₃, R₄ are H, and R₅ is COOCH₃, which is methyl2-O-(3,4,5-trimethoxycinnamoyl)corosolate (6).
 7. The corosolic acidanalog of the formula I, as claimed in claim 1, wherein R₁ and R₂ aretaken together to form SO₂, R₃, R₄ are H, and R₅ is COOH, which is2α,3β-dihydroxyurs-12-en-28-oic acid 2,3-cyclicsulphate (7).
 8. Thecorosolic acid analog of the formula I, as claimed in claim 1, whereinR₁, R₂, R₃ and R₄ are H, and R₅ is CONH₂, which is corosolamide (8). 9.The corosolic acid analog of the formula I, as claimed in claim 1,wherein R₁, R₂, R₃ and R₄ are H, and R₅ is CONHPh, which isN-phenylcorosolamide (9).
 10. The corosolic acid analog of the formulaI, as claimed in claim 1, wherein R₁, R₂, R₃ and R₄ are H, and R₅ isCONHCH₂CH₂NH₂, which is N-(2-aminoethyl)corosolamide (10).
 11. Thecorosolic acid analog of the formula I, as claimed in claim 1, whereinR₁, R₂, R₃ and R₄ are H, and R₅ is CON(CH₂CH₂)₂NH, which isN-corosolylpiperazine (11).
 12. The corosolic acid analog of the formulaI, as claimed in claim 1, wherein R₁, R₂, R₃ and R₄ are H, and R₅ isCONHCH₂CH₂OH, which is N-(2-hydroxyethyl)corosolamide (12).
 13. Thecorosolic acid analog of the formula I, as claimed in claim 1, whereinR₁ and R₂ are COCH₃, R₃ and R₄ is H, and R₅ is COOCH₃, which is methyldiacetylcorosolate (14).
 14. The corosolic acid analog of the formula I,as claimed in claim 1, wherein R₁ and R₂ are H, R₃ and R₄ together formO, and R₅ is COOCH₃, which is methyl 11-ketocorosolate (15).
 15. Thecorosolic acid analog of the formula I, as claimed in claim 1, whereinR₁ and R₂ are COCH₃, R₃ and R₄ together form O, and R₅ is COOCH₃, whichis methyl diacetyl-11-ketocorosolate (16).
 16. The corosolic acid analogof the formula I, as claimed in claim 1, wherein R₁ and R₂ are H, R₃ andR₄ together form O, and R₅ is COOH, which is 11-ketocorosolic acid (17).17. The corosolic acid analog of the formula I, as claimed in claim 1,wherein R₁ and R₂ are COCH₃, R₃ and R₄ together form O, and R₅ is COOH,which is diacetyl-11-ketocorosolic acid (18).
 18. The corosolic acidanalog of the formula I, as claimed in claim 1, wherein R₁ and R₂together form SO₂, R₃ and R₄ together form O, and R₅ is COOH, which is2α,3β-dihydroxyurs-12-en-11-one-28-oic acid 2,3-cyclicsulphate (19). 19.The corosolic acid analog of the formula I, as claimed in claim 1,wherein R₁ and R₂ are H, R₃ and R₄ together form O, and R₅ is CONH₂,which is 11-ketocorosolamide (20).
 20. The corosolic acid analog of theformula I, as claimed in claim 1, wherein R₁, R₂ and R₃ are H, R₄ is OH,and R₅ is CONH₂, which is 11-hydroxycorosolamide (21).
 21. The corosolicacid analog of the formula I, as claimed in claim 1, wherein R₁, R₂ andR₃ are H, R₄ is OH, and R₅ is COOCH₃, which is methyl11-hydroxycorosolate (22).
 22. The corosolic acid analog of the formulaI, as claimed in claim 1, wherein R₁, R₂, R₃ and R₄ are H, and R₅ isCHO, which is corosolinal (24).
 23. The corosolic acid analog of theformula I, as claimed in claim 1, wherein R₁, R₂, R₃ and R₄ are H, andR₅ is COOCOC₆H₂(OCH₃)₃, which is corosolyl tri-O-methylgallate (25). 24.The corosolic acid analog of the formula I, as claimed in claim 1,wherein R₁, R₂ and R₃ are H, and R₄ and R₅ together to form OCO, whichis 2α,3β-dihydroxyurs-12-en-11,28-olide (26).
 25. A process forproducing corosolic acid analogs of the formula I comprising the stepsof extracting leaves of Lagerstroemia species with water, alcohol orpolar organic solvents, chromatographically purifying said extract toabout 95% purity and converting said corosolic acid to novel analogs byintroducing new functional groups therein, in a known manner.
 26. Apharmaceutical composition containing at least one corosolic acid analogas claimed in claims 1 to 24 and a pharmaceutically acceptable carrier.27. The pharmaceutical composition as claimed in claim 26 wherein saidcarrier is an aqueous or non-aqueous carrier.
 28. A method of treatingdiabetes, inflammatory and tumor diseases comprising the steps ofadministering one or more corosolic acid analogs of the formula I.